The US has long demanded all NATO nations spend a minimum of 2% of their GDP annually on the military. Many nations don’t meet this level, and many have said they have no intention of doing so. Since the alliance controls most of their neighbors, they really don’t have a need for a big military.

Trump singled out Germany in particularly, saying the country “has not contributed what it should be contributing” to military spending. German officials have made clear they have no intention of spending 2% of their GDP on military, and argue that funds for foreign aid should count just as much.

Many European NATO nations say they really don’t have the infrastructure to realistically spend that much on their militaries anyhow, and don’t have arms industries to support such large forces. It has been speculated that the US interest in forcing these increases is, at least in part, about selling more US weapons across the alliance.